It takes two to tango and these tacos will find you wanting seconds. Use steak, mango and salsa for a unique taco meal.
Cut beef steak lengthwise in half, then crosswise into 1/4-inch thick strips. Combine beef and taco seasoning mix in medium bowl; stir to coat beef.
Heat 1 teaspoon oil in large, nonstick skillet over medium-high heat until hot. Add half of beef; stir-fry 1 to 2 minutes or until outside of beef is no longer pink. Remove from skillet. Repeat with 1 teaspoon oil and remaining beef. Set aside; keep warm.
Heat remaining 1 teaspoon oil in same skillet until hot. Add onion; cook 2 to 3 minutes or until tender. Return beef to skillet; cook 1 minute or until heated through.
Place equal amounts of steak and onion on each tortilla; top with lettuce, cheese, salsa and mango.